Method of gas plating



p 1959 P. R. MARVIN 2,905,573

METHOD OF GAS PLATING Filed Dec. 10, 1957 TO VACUUM PUMP INVENTOR PHIL /P R MARV/N ATTORNEY United States Patent 1 2,905,573 "METHOD OF GAS PLATING Philip Roger Marvin,-Fairfield, Conn., assignon byi-mesne assignments, .to :Union Carbide=Corporation, New ork,

N;Y., :a corporation ofNew York Application December .10, 1$57,-Seriali-No.:7.01,776 7 Claims. *(Cl. 117- 60) This invention relates to --the production of metallic articles and particularly to articles of irregular's'hape; more specifically the invention relates the production of articles which include asan important constituent the "higher melting -point metals such as tungsten and molybdenum.

A primary object of'the inven'tionis todescribe anove'l process for the production of metallic objects such as frames, tr im, angles, stripings, springs and combinations 0f these. 'The process o'f' the invention particularly .contemplates the provision-on a combustible material of a iheat-conductive film, the heating o'f th'is film in a vacuum -or in-a cham'ber evacuated to an extent 'such that the heat :does not cause the combustible material to be consumed, the contacting of the film with'a heat-decomposa'ble gaseous compound which is decomposable at the temperature "of the film to deposit ametal thereon, the rem'oval of the :supported metal fromthe "vacuum, and the burning of the combustible material from the metal :constituting th'e article.

This application is a continuation-in-part of co-pend- :ing application iSerial No. 4 1K895, filed March '22, 1954, lnowsRatent No 2,83 4g69flpissued May 13,1958, assigned -to -:the vsame fassignee as ithe :present invention.

The combustible :material, :esg. icellulosic or t't'he like, may :he substantially planar, zthat is, for example a sheet of :paper. :Gr -'.the:ma'te'rial may. suitably be three-dimen- :sional, :a box for instance. 'IIn t either aevent the "surface :or surfaces :thereof are veryilightly :coated .with Ithe heatconductive film which is formed :th'ereon in :a :desired configuration. The film is :most ssu'itabl-y :fonned 0f a metallic paint, erg. ;aluminum, :or -:a printing'lirik (the carbon of which is electrically conductive); the .film may :thus he simply painted, :sprayed cor Ecoated i011 ethe combustible :material in any ssuitablemanner. The-shape of the .object'ztohe formedeis substantially immaterial tfor practically any shape :be arranged to have an-filrnzthereomcontacted byttirezheatdecomposable gas. The -invention *however finds :its greatest utility where the shapetis relatively tcomplicated or where-the metal of which the article is constituted, in whole .-:or in .part, has a high melting gpoint and consequently a :high temperature ifor working, :drawing, :rolling and so -.:forth .under normal {Processing -conditions.

:Articles formed "under theiconditions :outlined have -..a decided advantage with respect to the purity :of --the metallic constituenh:overtmostother;tpr.ocesses. Further the metal -is -:not subjected -,during processing :to .1 arduous mechanical working and accordingly :the ;:products have desirable physicakqualities of strength, ductility,elasticity and so on, depending upon .th-emature of the articleritself.

-The invention will be more -fullyxunderstood eby the following .detailed .description rand "accompanying-draw- .ings wherein specific examples .of articles produced :in accordance with the invention :are set .forthby way .of illustration only and arenot to be construed as limitative of. the inventive concept.

In the drawings- Figure 1 illustrates an appartus arrangement .useful in the practice of 'the'inven'tion;

Figures 2 and 2Aillustrate, respectively, a-blank and the product producible from the' blankzin 'the practiee of 'the invention;

Figures 3 and 3A illustrate, respectively, a .blank for the production of an article in accordance with the practice of the invention and the article 'producible therefrom;

Figures 4 and -4A illustrate, respectively, a blank "for the production of a spring and the spring itself in accordance with the principles of this invention;

Figures 5 and 5A illustrate, respectively, a blank 'and a three-sided article producible from the blank :in accordance with the principles of 'theinvention; and

Figure 6 illustrates a network produced ofmetal in accordance with the invention.

Referring to the drawings 'there is shown in Figure =1, a glass 'vessel surrounded -by a water jacket 3 having inlet 5 'and outlet 7 and adapted to maintain the interior walls ofthe vessel cool. Vessel -1.'has'c'losing portions 9, tightly and removably sealed thereto with the :aid of gaskets 13, 15.

Closing portion 9 has, preferably integral therewith, a gas inlet line 17 having-valve 1'9 which-is adapted when opened to permit a -flow-of plating gas therethrough to the interior of vessel '1.

Closing portion 11 has, also preferably integral therewith, 'a gas outlet line 2-1 for the passage of gases outwardly from the vessel '1. This line 21 communicates through a suitable -L-shaped coupling with conduit 23 which terminates in a'U-shaped portion 25 which extends through a cololing liquid, as Dry'Ice and acetone, in trap '27. Avacuum pump (not shown) is adapted-to produce a-vacuum in the apparatus and to .draw exhaust gases .to the trap.

Positioned in the vessel "1 onasuitablebase zof insulating material29 is a heavy cardboard 31 having a 'metal film 33,'on the'upper surface thereof, -a coating of aluminum paint; the cardboard 31 is in the shape illustrated in Figures'S 'and 3A and is in-the form of an ordinary electric switch plate, which plate has therethrough a'central opening 35 through which the actuating member of the switch passes. 'Alsoprovided at 37 are openings for the receipt of holding means such as screws for fastening the plate-to a wall.

The metal'film 33 on the cardboard 31 is adaptedto'be heated'by means of an-induction coil 39 which surrounds thevessel g1 and'water jacket Sand is provided with energy from a-source not shown.

In the operation-ofthe apparatus -valve 1'9"is closed-the vacuum pump is operated and energy :is -supplied to the coil 39-to"heat the film -33. Thisprocedureetfectscomplete evacuation of the "apparatus prior to the production of "the plating gas itself.

Whenthe apparatus'hasbeen completely evacuated the valve 19 is opened withthevacuumpumpstilloperating and a flow ,of plating gas enters throughline, 17 to contact the [film 133.

A mostsuitable.pIating gasis .nickel-,carbonyl as the nickel tfilm= deposited therefrom on the .film 33 provides a. fine t-finish which 1is .non-;corrosive and does .not require further treatment. However the plating gas may heany of those :indicated in .the ..following table, which sisvset forth :byzwvay :of example zonl-y:

.. Temperature "System range'of base Plating matenal pressure, materialrin .mm. vof Hg degrees Fahrenheit;

N K00); 0;5''110' 350-450 0. 5-1: 8. g375e4'50 0. 571.8,. 1150-650 0. 5+1f8 525-775 0 5-118? 400-750 It will be noted that for the nickel carbonyl the temperature of the film 33 should be at least about 350 F. when the plating gas enters the chamber of vessel 1. Preferably the temperature is somewhat higher, but not above the maximum indicated of 450 F., as higher temperatures than this ofier no advantages. The heavy cardboard 31 will not be seriously affected by the temperature and will not burn since there is substantially no air in the chamber.

The plating is continued for a period of time sufficient to efiect deposition of about V8 of an inch of metal over the film 33. Thereafter the heat energy to the film is cut ofi and the work cooled before removing it from the chamber.

In order to assist in breaking the vacuum within the vessel 1 a conduit having a valve 20 may be connected to a source of carbon dioxide and when valve 19 is cut oft CO may be put through the chamber to clear out any remaining heat-decomposable carbonyl and to provide a pressure in the chamber which permits of readily opening the same.

. After removal from the apparatus the cardboard is fired at low temperature in the air and is burned from the metallic plate which remains. In the case of aluminum paint combustible constituents of the paint itself will also be removed and the film of aluminum will ordinarily be so thin as to be substantially indistinguishable on the plate back. The completed product will then have the configuration indicated in Figure 3A.

In a further embodiment of the invention the spring shown in Figure 4A may be produced by forming a hollow cylinder 41 of cardboard of considerable wall thickness and lightly forming a spiral groove in the internal surface 43 thereof as at 45. I

A sharp tool carrying aluminum paint on the end thereof is then inserted in the hollow of the cylinder and the groove is painted as indicated at 47. This coil is then placed in the apparatus of Figure l and heat applied until the very thin aluminum film attains a temperature in the range of 525-775 F. The vacuum pump is operated with valves 19 and 20 closed in order to insure of complete evacuation of the equipment and of any gases formed from the paint film; upon completion of the evacuation valve 19 is opened to introduce tungsten carbonyl into the apparatus to provide a pressure of carbonyl therein of about one mm. of mercury. The carbonyl enters the hollow of the cylinder, contacts the paint and deposits thereon to form a spiral of metal. This spiral of metal may be of considerable thickness, and it is to be understood that the original paint thickness has little to do with the ultimate metal thickness deposited, the initial film serving merely as a heat-conductive pattern upon which the metal of the gas deposits. The resultant product of the plating operation when cooled and fired, and removed therefrom, is a coil spring such as shown at 49 in Figure 4A.

Referring briefly now to Figures 2 and 2A the angle iron is producible from the film 53 which is painted on achieving a desired result. Fabric may also be employed and an open net structure is useful in the production of an open metal network or grid such as is shown in Figure 6 at 63. Combinations of the cardboard or the like cellulosic material, fabricor other easily combustible material may be utilized to achieve particular results.

The process of invention is applicable to intricate shapes as will be noted from the specific examples set out hereinbefore and is of particular utility in the deposition of the high melting point metals because of the difiiuclties which are inherent to the normal working processes of the same. The products in each case are smooth finished, bright and in general corrosion resistant due to their purity.

It will be understood that this invention is susceptible to modification in order to adopt it to dilierent usages and conditions and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

What is claimed is:

1. In a method of producing metal articles the steps of providing a combustible support, applying on said combustible support a heat-conductive film having substantially the shape of the article to be formed, heating said film shape in an evacuated atmosphere at a temperature of between about 350-450 F. at which temperature the support is not consumed, contacting the heated film shape with gaseous nickel carbonyl to cause the same to decompose and deposit nickel metal thereon, removing the support and resultant metal deposited film from the evacuated atmosphere, and burning off the support to recover a metal article of the shape of said heat-conductive film.

2. In a method of producing articles of chromium, the steps of providing a combustible support, applying on said combustible support a heat-conductive film having substantially the shape of the article to be formed, heating said fihn shape in an evacuated atmosphere at a temperature of between about 375-450" F. at which temperature the support is not consumed, contacting the heated film with gaseous chromium hexacarbonyl to cause the same to decompose and deposit chromium thereon, removing the support and resultant metal deposited film from the evacuated atmosphere, and burning otf the support.

' 3. In a method of producing articles of tungsten, the steps of providing a combustible support, applying on said combustible support a heat-conductive film having substantially the shape of the article to be formed, heating the film in an evacuated atmosphere at a temperature of between about 525-775 F. at which temperature the support is not consumed, contacting the heated film with gaseous tungsten hexacarbonyl to cause the same to heatthe box 55 of Figure 2, 1n the same manner as described hereinbefore, and the metal may be any of those derivable from the compounds indicated in the table set out above.

The structure of Figure 5A which is producible from the blank of Figure 5 illustrates a material having three sides 57a, 57b and 570. To produce this a box 59 is painted as at 61a, 61b and 610, support for the latter film (610) being a cutout portion of the cardboard box. The structure of Figure 5A may be slit at the vertical edge 57d and the edges bridged by contact of gas with the adjacent edges during the plating operation. If desired the lateral edge may be cut sufficiently remote from the forward edge to avoid such bridging.

The cardboard material is most flexible and may be formed into an indefinite number of shapes and may be rolled or otherwise mechanically worked to insure of decompose and deposit tungsten thereon, removing the support and resultant tungsten deposited film from the evacuated atmosphere, and burning off the support to recover a tungsten article of the shape of said heat-conductive film.

4. In a method of producing articles of molybdenum, the steps of providing a combustible support, applying on said combustible support a heat-conductive film having substantially the shape of the article to be formed, heating the film in an evacuated atmosphere at a temperature of between about 450-650 F. at which temperature the support is not consumed, contacting said heated film with gaseous molybdenum hexacarbonyl to cause the same to decompose and deposit molybdenum thereon, removing the support and resultant molybdenum deposited film from the evacuated atmosphere, and burning off the support.

5. In a method of producing articles of copper, the steps of providing a combustible support, applying on saic l combustible support a heat-conductive film having substantially the shape of the article to be formed, heating the film in an evacuated atmosphere at a tempera ture of between about 400-75 0 F. at which temperature the support is not consumed, contacting said heated film with gaseous copper carbonyl to cause the same to decompose and deposit copper thereon, removing the support and resultant copper deposited film from the evacuated atmosphere, and burning off the support.

6. In a method of producing metal articles, the steps of providing a combustible support, applying on said combustible support a heat-conductive film having substantially the shape of the article to be formed, heating said film shape in an evacuated atmosphere at a temperature of between about 350-450 F. at which temperature the support is not consumed, contacting the heated film shape with gaseous metal bearing compound selected from the group consisting of chromium carbonyl,

tungsten carbonyl, molybdenum carbonyl, copper carbonyl and nickel carbonyl to cause the said metal bearing compound to decompose and deposit the metal constituent thereon, removing the support and resultant metal deposited film from the evacuated atmosphere, and burning ofi? the support to recover a metal article of the shape of said heat-conductive film.

7. As an article of manufacture, a product made in accordance with the method set forth in claim 6.

References Cited in the file of this patent UNITED STATES PATENTS 2,619,433 Davis et al. Nov. 25, 1952 2,694,652 Loonam Nov. 16, 1954 2,834,690 Marvin May 13, 1958 

1. IN A METHOD OF PRODUCING METAL ARTICLES THE STEPS OF PROVIDING A COMBUSTIBLE SUPPORT, APPLYING ON SAID COMBUSTIBLE SUPPORT A HEAT-CONDUCTIVE FILM HAVING SUBSTANTIALLY THE SHAPES OF THE ARTICLE TO BE FORMED, HEATING SAID FILM SHAPE IN AN EVACUATED ATMOSPHERE AT A TEMPERATURE OF BETWEEN ABOUT 350-450*F. AT WHICH TEMPERATURE THE SUPPORT IS NOT CONSUMED, CONTACTING THE HEATED FILM SHAPE WITH GASEOUS NICKEL CARBONYL TO CAUSE THE SAME TO DECOMPOSE AND DEPOSIT NICKEL METAL THEREON, REMOVING THE SUPPORT AND RESULTANT METAL DEPOSITED FILM FROM THE EVACUATED ATMOSPHERE, AND BURNING OFF THE SUPPORT TO RECOVER A METAL ARTICLE OF THE SHAPE OF SAID HEAT-CONDUCTIVE FILM. 